A seroma is accumulation of clear fluid in the body after surgery. It is a common complication which can occur in the underarm area (axilla) after breast or axillary surgery. In fact, axillary seromas have been seen even after axillary lymph node biopsy or sentinel lymph node biopsy for breast cancer

To prevent seroma formation, surgeons insert drains after breast and axillary surgery ( both cancerous and non cancerous). Drains are usually removed once the output falls below 40 cc for two consecutive days. Early removal of drains is a common cause which can predispose to seroma formation after breast cancer surgery. 

Patients usually develop fluid collections within 5-7 days after surgery and they present with pain and swelling in the axillary region. Diagnosis of a seroma can be made by your breast cancer surgeon and in case of any doubt, an axillary ultrasound can confirm the diagnosis.

Management of an axillary seroma is relatively simple. They can be aspirated under local anaesthesia. Patients might require 2-3 aspirations before the seroma subsides.

Sometimes fluid collections can become infected and can give rise to pus formation in the axillary region. These situations can be avoided if seromas are detected and aspirated in time.